everettengr
Aluminum
- Joined
- Dec 14, 2011
- Location
- san diego
My 10EE came with an obsolete and badly matched solid-state drive that had a speed range of only 600-1000 RPM. It had little or no effective feedback control, meaning it slowed heavily even with moderate cuts. I knew my 10EE had been able to do much better on the Argon-thyristor 'Modular' drive, so I attempted to restore that.I was not able to make it fully functional. Eventually, I got tired of chasing gremlins and gave up to try a newer and better solid-state DC drive.
I made the decision to keep the DC motor in lieu of AC/VFD because DC motors and controls offer distinct mechanical advantages for a lathe compared to AC motors. Torque and speed are controllable independently and over the entire range from zero to maximum ratings (torque proportional to current supplied, speed proportional to voltage). This is well-matched to lathe applications, where various speeds-and-feeds requirements reflect back to the prime mover as motor speed and torque requirements.
Peak and short-term delivered power can be multiples of the continuous rating. This is also well-matched to machining, with short periods of heavy cutting interspersed with lighter cuts.
While a DC motor has nominal, or “nameplated” HP and torque ratings, it can deliver and sustain multiples of that power for short periods, subject primarily to heat dissipation and mechanical limits. A 5 HP DC motor can replace a stock AC motor rated from 7.5 to 10 HP. The DC motor control converts the AC input power to a variable voltage and current-limited DC supply, typically through a switched rectifier design.
For all their advantages, DC motors are not used as much these days for machine tools because the motors themselves became too expensive. Brushed designs also require periodic maintenance for brush inspection and replacement and commutator refinishing.
However, in my case, I already had the DC motor and was advised that new-old-stock SSD drives are very affordable, so why convert to a less advantageous AC design???
I made the decision to keep the DC motor in lieu of AC/VFD because DC motors and controls offer distinct mechanical advantages for a lathe compared to AC motors. Torque and speed are controllable independently and over the entire range from zero to maximum ratings (torque proportional to current supplied, speed proportional to voltage). This is well-matched to lathe applications, where various speeds-and-feeds requirements reflect back to the prime mover as motor speed and torque requirements.
Peak and short-term delivered power can be multiples of the continuous rating. This is also well-matched to machining, with short periods of heavy cutting interspersed with lighter cuts.
While a DC motor has nominal, or “nameplated” HP and torque ratings, it can deliver and sustain multiples of that power for short periods, subject primarily to heat dissipation and mechanical limits. A 5 HP DC motor can replace a stock AC motor rated from 7.5 to 10 HP. The DC motor control converts the AC input power to a variable voltage and current-limited DC supply, typically through a switched rectifier design.
For all their advantages, DC motors are not used as much these days for machine tools because the motors themselves became too expensive. Brushed designs also require periodic maintenance for brush inspection and replacement and commutator refinishing.
However, in my case, I already had the DC motor and was advised that new-old-stock SSD drives are very affordable, so why convert to a less advantageous AC design???